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Weight Loss and Diet Pills: Options to Know

Medically reviewed by L. Anderson, PharmD. Last Updated on Apr 13, 2018.

What Are Weight Loss Drugs?

Prescription weight loss pills, also called anti-obesity drugs or “diet pills”, are sometimes prescribed to a patient as an additional tool in the treatment for weight loss. Tools added to medication treatment usually include a plan for lower fat and calorie foods, as well as a regular exercise program.

Most weight loss drugs that suppress the appetite are known as anorexiants. Some weight loss drugs contain a stimulant medication and are classified as controlled substances by the Drug Enforcement Agency (DEA). In 2012, the FDA approved the first two new weight loss drugs in over a decade -- Belviq and Qsymia. Since that time, several more new weight loss medications have been approved, including Contrave, Saxenda, and Belviq XR.

Patients who are overweight or obese with any health condition should consult with their physician prior to beginning a weight loss or exercise program.

There are very few proven choices in over-the-counter (OTC) or nonprescription medications for effective weight loss. One agent that is available without a prescription is Alli (orlistat), a lower-dose version of the prescription drug Xenical.

Many people who are trying to lose weight may attempt to use dietary supplements or herbal medications, but most of these products have not been adequately studied for effectiveness or safety and none are approved by the U.S. Food and Drug Administration (FDA) for weight loss. Check with a healthcare provider for advice before using herbal or dietary supplements for weight loss.

How Much Weight Can I Lose With Diet Pills?

Prescription weight loss drugs may be an option for patients who have serious health risks, such as high blood pressure, type 2 diabetes, or high cholesterol and cannot control their weight with diet and exercise alone. Weight loss drugs should not be used as a substitute for healthful eating and a regular exercise program.

Over one year, patients using weight loss drugs may lose roughly 5% to 10% of their initial weight when used as part of a diet and exercise plan. However, for most weight loss drugs, if you have not lost at least 5% of your initial body weight after 12 weeks, it is unlikely that you will achieve and sustain clinically meaningful weight loss with continued treatment.

Common "Diet Pills" or Weight Loss Drugs

Brand Name Generic Name Description Controlled Substance?

Adipex-P

Phentermine Appetite suppressant; anorectic Yes, DEA schedule IV
Alli Orlistat Lipase inhibitor; inhibits fat absorption in the intestine No, available over-the-counter (OTC)
Belviq, Belviq XR Lorcaserin Selective serotonin 2C receptor agonist; promotes a feeling of fullness or satiety Yes, DEA schedule IV
Bontril PDM Phendimetrazine Appetite suppressant; anorectic Yes, DEA schedule III
Desoxyn Methamphetamine Appetite suppressant; use cautiously if prescribed for weight loss due to high potential for abuse, illegal distribution Yes, DEA schedule II
Didrex Benzphetamine Appetite suppressant; anorectic Yes, DEA schedule III
Diethylpropion Diethylpropion Appetite suppressant; anorectic Yes,  DEA schedule IV
Meridia Sibutramine Anorectic; withdrawn from US market in 2010 due to increased heart risk. Not available
Qsymia Phentermine and topiramate extended-release capsules. Combination appetite suppressant-anorectic; exact action of topiramate on weight loss is not known Yes, DEA schedule IV
Suprenza Phentermine Appetite suppressant; anorectic Yes, DEA schedule IV
Xenical Orlistat Lipase inhibitor; prescription form of Alli (OTC); higher dose than Alli; inhibits fat absorption in the intestine No
Contrave Bupropion hydrochloride-naltrexone hydrochloride Increases metabolism, suppresses appetite, affects central reward center (proposed mechanism) No
Saxenda Liraglutide GLP-1 may regulate areas of brain involved in appetite (proposed mechanism) No

How Effective Are Weight Loss Drugs?

Weight loss drugs don't always work for everyone. It is usually recommended that one to two pounds of weight can be safely lost per week.

  • Weight loss drugs typically result in a 5% to 10% weight loss over a 12-month period when used as part of a diet and exercise plan.

For a patient weighing 200 pounds, this would translate into losing about 10 to 20 pounds over one year, which would fall within the safe guidelines for weight loss. While this amount of weight loss seems small, it may be enough to help lower blood pressure or have a positive effect on blood sugar.

Learn More: 5 Diet Drugs: Which Ones Work?

Who Should Use Weight Loss Drugs?

Generally, most overweight people should initially try to lose weight using diet and exercise. Prescription diet pills are used in more severe circumstances, when weight loss has not been successful and the patient has important health risks associated with being overweight or obese. However, diet and exercise should always be used in conjunction with prescription weight loss drugs.

Most prescription weight loss drugs note in the package labeling that a person should meet certain requirements, such as a specified body mass index (BMI) and/or have a serious medical risk before using the drug.

Weight loss drugs are usually indicated for obese patients with an initial body mass index (BMI) greater than 30 kg/m2 or overweight patients with a BMI greater than 27 kg/m2 in the presence of other risk factors (eg, high blood pressure, type 2 diabetes, high cholesterol).

Examples of serious medical risks include:

To help assess your health risk based on weight, calculate your body mass index (BMI) here.

Should I Try to Lose Weight If I Am Pregnant?

A certain amount of additional weight gain, and no weight loss, is currently recommended for all pregnant women, including those women already overweight or obese.

Weight loss drugs should not be used during pregnancy. All weight loss drugs fall under pregnancy category X and are contraindicated (meaning do not use) in pregnancy. Weight loss offers no potential benefit and may result in fetal harm during pregnancy. Talk to your doctor about how much weight you should gain during pregnancy, and how quickly.

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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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